JPS6010265A - Electrophotographing method - Google Patents

Abstract

PURPOSE:To eliminate a memory effect by setting the flow-in current of DC corona discharge in the stage of transfer when a photosensitive layer consisting of an org. photoconductor is used. CONSTITUTION:The image part of a photosensitive layer 3 consisting of an org. photoconductor is positinely electrostatically charged and a toner 6 negatively electrostatically charged is stuck thereto. Copying paper 11 is superposed thereon and is charged to plus by a charger 8 in a transfer stage B. The generation of the toner 6'' positively charged by the plus charge throughout the paper 11 is prevented by setting the DC corona charge during transfer at the flow-in current of 23-35 times the influx current at the start of transfer. The electrostatic charging of the toner to a uniform polarity in the succeeding destaticization stage C is thus made possible and the memory effect by the toner 6'' is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic method using an organic photoconductor photosensitive layer, and more particularly, various operations of electrostatic image formation, toner development, transfer, and cleaning on the photosensitive layer. The present invention relates to an electrophotographic method in which the memory effect observed when repeating is eliminated and clear images are always formed.

In the present invention, an organic photoconductor photosensitive layer having dual charging characteristics is subjected to main charging by direct current corona discharge and image exposure, and the electrostatic charge that is formed is developed with a magnetic brush of toner. In an electrophotographic method, toner is transferred from the back of the copy paper by direct current corona discharge of the same polarity as the main charge by bringing the layer into contact with the copy paper, and the photosensitive layer after the transfer is cleaned with a magnetic brush after static electricity is removed. Direct current corona discharge is performed by setting the inflow current to 26 to 65 times the inflow current value at the start of transfer, and the photosensitive layer after transfer is subjected to direct current corona discharge of opposite polarity to the main charging to make the residual toner uniform in polarity. The present invention relates to an electrophotographic method characterized by charging.

In FIG. 1 for explaining the electrophotographic method to which the present invention is directed, a photoconductor photosensitive layer 6 is provided on the surface of a conductive substrate 2 of a driving rotary drum 1. As shown in FIG.

Along the surface of the drum 1, a main charging DC corona charger 4, an image exposure optical system 5, a magnetic brush development and cleaning mechanism 7 for holding toner 6, a transfer DC corona charger 8, and a static neutralization DC corona charger 9 are arranged. and a static eliminating light source 1o are provided in this order.

During copying, the photosensitive layer 3 is charged to a constant polarity by the main charge 4, and imagewise exposed through the optical system 5 to form an electrostatic image corresponding to the original image. A toner 6 charged with a polarity opposite to that of the electrostatic image is used and a magnetic brush 7 of this toner is used to rub the photosensitive layer, thereby forming a toner image corresponding to the electrostatic image on the photosensitive layer.

Supplying copy paper 11 on the surface of the photosensitive layer having the toner image,
A transfer charger 8 charges the copying paper 11 with the same polarity as the electrostatic image from the back side of the copying paper 11, and transfers the toner image to the surface of the copying paper 11. The copy paper on which the toner image has been transferred is separated from the photosensitive layer 6 and sent to a fixing mechanism (not shown) 1-1 to produce a copy on which the toner image has been fixed.

After the toner image is transferred, an amount of toner remains in the photosensitive layer depending on the transfer efficiency. These toner particles are unevenly charged because they have undergone a transfer process. In order to make the charged charges uniform, DC corona charging with a polarity opposite to that of the main charge is performed by the charger 9, and in order to further remove the charge remaining on the photosensitive layer, the entire surface is exposed to light from a static elimination light source 10. . In this state, the photosensitive layer 3 is rubbed by the magnetic brush 7, and the charged toner particles on the photosensitive layer 6 are attracted onto the magnetic brush, completing the 11-ning process. , development is performed by the magnetic brush 7 during the first rotation of the drum, cleaning is performed using the same magnetic brush 7 during the second rotation of the drum, and one copying cycle is completed in two rotations of the drum. The required number of copies can be obtained by repeating the above cycle as many times as necessary on the drum that has been cleaned.

When this electrophotographic method is applied to a photosensitive layer of an organic photoconductor that can be charged in both directions, unlike the case of a photosensitive layer of a vocal photoconductor made of selenium, cadmium sulfide, etc., during image creation in the first cycle. It has been found that a serious drawback arises in that the memory appears after the second cycle. That is, the organic photoconductor photosensitive layer has a dielectric constant lower than that of the inorganic photoconductor;
This memory effect is thought to be due to the fact that a gear+1 gear is formed which has an extremely long lifetime, making toner transfer and cleaning removal difficult.

According to the research conducted by the present inventor, this memory effect appears to be based on the principle shown in FIG. In the developing process (/l) shown in FIG. 2, the image area of the photosensitive layer 6 is positively charged, and the negatively charged toner 6 is in this positively charged area.
is attached. Next, in the transfer step CB), the copy paper 11 is placed on the photosensitive layer N6, and a positive charge is applied from the back side thereof using the charger 8. As a result, the negatively charged toner 6 is transferred onto the copy paper 11, but at this time, due to the positive charge that passes through the copy paper 11, the toner formed...
6' is charged to substantially zero, and the other toner 6'' is positively charged L7, and these zero-charged toner 6' and positively charged toner 6'' remain on the photosensitive layer 6.

In the static elimination process (C), negative charging from the charge 9 and exposure for static elimination using the lamp 10 are performed,
The substantially zero-charged toner 6' is negatively charged, but the positively charged toner 6'' is hardly charged due to the cancellation of charges.

Next, in the cleaning step (υ), when the photosensitive layer 6 is brought into contact with the magnetic brush 7, the negatively charged toner 6' is attracted to the magnetic brush by the Coulomb force between it and the magnetic carrier, but uncharged particles and toner 6'', such a force is not generated, so that it remains on the photosensitive layer 6.

In the main charging process (E), when the photosensitive layer 3 where this toner 6'' remains is positively charged from the charger 4, the positive charging is effective in the areas where the toner has been completely cleaned. Toner 6
In the area where " remains, positive charging is performed only weakly, and in the next development and transfer process, this toner 6"
Only a low-density image is formed in the area, which means that there is no image.

Due to the occurrence of such a memory effect, a portion of the photosensitive layer corresponding to a solid black area in the -th cycle appears as an image with a significant decrease in density in the second cycle.

According to the present invention, the DC corona discharge at the time of transfer is performed by setting the inflow current to 26 to 65 times the transfer start inflow current value, so that the polarity of the transfer corona discharge is strongly maintained in the transfer step CB). Preventing the generation of charged toner particles 6'', allowing the residual toner particles to be charged to a uniform polarity in the static elimination step (C), and causing all the residual toner to be attracted to the magnetic brush, This eliminates the memory effect mentioned above.

Now, if we plot the relationship between the set inflow current of the transfer corona charger and the toner transfer efficiency, in the case of an organic photoconductor photosensitive layer that has both charging characteristics, we will get a curve as shown in A in Figure 3. . That is, toner transfer begins to occur from a certain transfer start inflow current value (Io) for a certain photosensitive layer, and from then on, as the current value increases, 1.
When the I-ner transfer efficiency increases and the inflow current value exceeds the value, the transfer efficiency no longer increases and becomes saturated at the value. This transfer start inflow current value (mu) is
Although it differs depending on the individual photosensitive layer, the overall trend is similar to curve A, and the saturation value of transfer efficiency is generally 6.
It ranges from 5 to 75%.

On the other hand, the relationship between the set inflow current of the transfer corona charger and the toner transfer efficiency in the case of an inorganic pre-electrode R3 optical layer such as selenium is as shown in curve B in FIG. Toner transfer is started at a current CIO') lower than the transfer start inflow current value Cl0) of the layer, and saturation of the toner transfer efficiency occurs at a current value larger than in the case of an organic photosensitive layer, and the saturation value of this transfer efficiency reaches a size of 90 to 97 inches.

Thus, in the conventional toner transfer system, transfer efficiency has generally been increased by setting the inflow current of the transfer charger to 40 to 66 times the transfer start inflow current value.

However, when such a set inflow current is used for toner transfer from an organic photosensitive layer, toner transfer may be performed with maximum efficiency, but adverse effects may occur due to reverse charging of toner remaining in the photosensitive layer. As already pointed out. On the other hand, in the present invention, the set inflow current is set to I. By performing toner transfer at 26 to 65 times as much as 26 to 65 times, the adverse effects of reverse charging on the toner remaining in the photosensitive layer are eliminated without substantially lowering the toner transfer efficiency.

In the present invention, this set inflow current is I. When it is smaller than 26 times of K, there is a tendency for image density to decrease due to a decrease in transfer efficiency and image disturbance due to poor transfer. If it is larger than 0.065 times, a memory effect due to reverse charging of the toner remaining in the photosensitive layer will appear.

In the present invention, it is difficult to directly measure the absolute value of the current flowing into the photosensitive layer of the transfer charger. But l
However, the current value can be set by positioning a metal surface instead of the photosensitive layer and actually measuring the current flowing from the charger at this time. In addition, for the transfer start inflow current value, set the inflow current value by the above-mentioned means, and plot the relationship between whether or not toner transfer occurs at this current value for each photosensitive layer and the transfer efficiency. You can easily see it by doing this.

Furthermore, the inflow current of the transfer charger can be set to a desired level by means known per se. For example, since this current is approximately proportional to the applied voltage of the charger, it can be set to the desired level by adjusting the applied voltage. In addition, this current decreases when the distance between the corona wire and the photosensitive layer is increased, and becomes the opposite when the distance between the corona wire and the photosensitive layer is increased.
．． In addition, this current can be adjusted by reducing the distance between the corona wire and the shield, decreasing the distance between the corona wire and the shield, and vice versa.

Although the method of the present invention is equally applicable to all organic photoconductor photolayers that are capable of being charged with both charges, it is applicable to organic photosensitive layers comprising a layer of a charge transport medium dispersion of a charge generating pigment on a conductive substrate. Particularly excellent effects are achieved when the As the charge-generating pigment, photoconductive organic pigments such as perylene pigments, quinacridone pigments, pyranthrone pigments, phthalocyanine pigments, disazo pigments, and trisazo pigments are used.On the other hand, as the charge transport medium, polyvinylcarbazole is used. Charge-transporting resins such as the above, and resins in which low-molecular charge-transporting substances such as hydrazone derivatives and pyrazoline basic conductors are dispersed are used.

The invention is illustrated by the following example.

Example (1) Production of photoreceptor The above weighed chemicals were placed in a stainless steel ball mill and the pulse rate was 6 minutes per minute.
Dispersion and dissolution were carried out at a speed of 0 rotation for 12 hours to obtain a uniform dispersion.

Next, add to the above dispersion liquid and perform dispersion and dissolution at a speed of 60 rotations for 4 minutes day and night to uniformly disperse the photosensitive liquid (made by 'A').
-It is.

This photosensitive liquid was coated on an aluminum drum having a diameter of 120 φ by dipping method, and dried for 1 hour in 11] QC to produce a photosensitive drum having a layer thickness of 12 μm after drying (7).

(11) Photoconductor test The photoconductor drums manufactured in (i) above were manufactured by Sanda Kogyo KK.
The transfer efficiency and the occurrence of memory were evaluated for each of the conditions, with the transfer charger installed in a DC-121 night photographic camera and the value of the current flowing into the drum of the transfer charger set to the following conditions. The results are shown in the table below.

Table Note] O: No memory generated ×: Memory generated Io: Transfer start inflow 1E current value = 1 μA As is clear from the above results, in the setting range of the inflow current value in the present invention (23<, 1/Io<35) Transfer efficiency could be maintained without causing memory.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram illustrating the electrophotographic process, FIG. 2 is a detailed diagram illustrating the present invention, and the Koro diagram is a diagram showing the relationship between the 1+11 current of the transfer charger and the transfer efficiency. 6...Photosensitive layer 4...Main charger 7...Developer borrowed 8...Transfer charger? ... Static elimination charger patent applicant Sanda Kogyo Co., Ltd. Figure 1 Figure 2

Claims (1)

[Claims] (1) The photosensitive layer of an organic photoconductor having dual charging characteristics is subjected to main charging by direct current corona discharge and image exposure, and the electrostatic image formed is developed with a magnetic brush of toner, and the photosensitive layer has a toner image. In an electrophotographic method, toner is transferred from the back side of the copy paper by direct current corona discharge of the same polarity as the main charge, and the photosensitive layer after the transfer is cleaned with a magnetic brush after static electricity is removed. Corona discharge is performed by setting the inflow current to 26 to 65 times the transfer start inflow current value, and the photosensitive layer after transfer is subjected to DC corona discharge of opposite polarity to the main charging to charge the residual toner to a uniform polarity. An electrophotographic method characterized by: